In a span of just 100 miles along the U.S.-Mexico border in California, two scenes played out Monday that symbolize the yawning chasm that is the national debate over immigration.

In the Imperial Valley, Vice President Mike Pence took a heavily secured tour of a construction site for the border barrier and lauded local Border Patrol agents, who presented him with a piece of the original border fence as a gift.

“With President Trump in the White House, I know you all know you have a leader who not only is listening to each and every one of you, and standing with each and every one of you, but he's also standing on the conviction that walls work,” Pence told the agents.

Meanwhile, a two-hour drive west, a caravan of Central American immigrants who have drawn the ire of Trump waited at the Tijuana-San Diego border crossing to ask for asylum. Many, including women and young children, slept overnight, on the ground, on the Mexico side after U.S. immigration officials said they had reached their capacity for processing immigrants without documents.

All this drew attention to California, which has been a consistent thorn in Trump’s side, especially in regard to immigration. The Trump administration has sued the state over its so-called sanctuary policies, and the president and Gov. Jerry Brown have sparred over plans to send members of the National Guard to the border.

Pence was greeted at Naval Air Facility El Centro on Monday morning by a small group of military personnel, some of whom had brought their children to meet him.

As Pence’s long motorcade traveled to an El Centro Border Patrol station along the Evan Hewes Highway, passing farmland and irrigation canals, residents emerged from houses, restaurants and shops to wave and flash thumbs up. Many whipped out their cellphones to snap photos.

A small group of protesters near the Border Patrol station held up signs, including one that read, “A border fence won’t save us.”

At the station, Pence thanked federal immigration agents for their work, telling them they have a “tireless champion of border security” in Trump.

Pence said that illegal crossings of the U.S.-Mexico border have decreased more than 40% over the last year. During a 20-minute speech, he repeatedly called agents and Customs and Border Protection employees heroes, saying they do a tough and dangerous job.

“Last year alone, across the Imperial Valley, El Centro agents seized 3.8 tons of illicit drugs in the midst of that rising violence against them,” Pence said. “But let me say, the assaults on our Border Patrol agents must end.”

Border Patrol Deputy Chief Carla Provost presented Pence with a piece of scrap metal from the area’s original border fence, which was built in the 1990s from steel airstrip mats left over from the Vietnam War.

Pence’s visit comes a little over a month after Trump toured border wall prototypes in Otay Mesa and less than two weeks after Homeland Security Secretary Kirstjen Nielsen visited Calexico’s border barrier. Nielsen also received a piece of the original border barrier.

Trump stirred confusion last month when he tweeted photos of the construction of the Calexico border barrier replacement, saying, "Great briefing this afternoon on the start of our Southern Border WALL!"

But plans for that project were begun in 2009, and Border Patrol agents had previously emphasized that it shouldn't be confused with Trump's wall.

In Calexico on Monday, Pence walked along a dirt path near the border with Provost and other officials as wind kicked dust onto his Oxford shoes. Workers lowered narrow sections of the barrier into place by crane, and an official told him the project is set to be finished by October.

Standing near the barrier, Pence said the construction represented “the kind of new border wall measures that we will be implementing all along the southern border.”

On the Mexicali side of the border, in a spot where no fence stood, a few dozen protesters in lime-green shirts held a large sign that read, “No al muro” — no to the wall. Ten Border Patrol agents on horseback separated them from Pence.

At the San Ysidro Port of Entry on Monday, Customs and Border Protection officials began to process members of the immigrant caravan who had arrived a day earlier to ask for asylum.

A CBP spokeswoman did not say how many migrants were being processed, but said the agency’s daily caseload varies depending on the complexity of the cases, the migrants’ medical needs and language barriers, and the amount of detention space available.

“As in the past when we’ve had to limit the number of people we can bring in for processing at a given time, we expect that this will be a temporary situation,” the spokeswoman said.

Activists said late Monday that eight people were being processed. Mothers and children were the first to be selected, according to an organizer: three mothers, four children and an 18-year-old were in the initial group.

Also on Monday night, the U.S. Department of Justice announced it had filed charges against 11 suspected caravan members, accusing them of entering the country illegally.

The suspects were arrested by members of the Border Patrol in areas west of the San Ysidro Port of Entry.

“When respect for the rule of law diminishes, so too does our ability to protect our great nation, its borders, and its citizens,” said Atty. Gen. Jeff Sessions in a statement.

But caravan leaders said they had no knowledge that any of its members were arrested.

An estimated 150 are expected to ask for asylum, a small percentage of the traveling group that organizers said at one point swelled to more than 1,700.

“Many of these families faced unspeakable violence and persecution in their home countries, separation from their families and an arduous journey over thousands of miles,” Laura Gault, an attorney for Human Rights First, said in a statement. “We hope that this development signals the end of the administration’s attempts to demonize the innocent.”

Pence said the migrants were “being exploited by open-border political activists and an agenda-driven media.”

Similar caravans have been organized before by a group called Pueblos Sin Fronteras, or People Without Borders. The caravans — which are safer than making the journey alone — are designed to raise awareness about the conditions that prompt people to flee and the dangers they face when they do.

In response to Pence, Alex Mensing, an organizer with Pueblo Sin Fronteras, said the families had fled their countries because of dire circumstances.

"It is very clear that the U.S. government is falsely citing capacity issues in order to deny asylum-seekers their due process," Mensing said. "The idea that they cannot process 150 refugees after more than 24 hours is ridiculous and shameful."

Speaking at a White House news conference Monday with Nigerian President Muhammadu Buhari, Trump said he had been paying attention to the caravan and that “we’re working on the border with the worst laws.”

“We need a wall, No. 1,” he said.

Castillo reported from Calexico and Branson-Potts from Los Angeles. Times staff writer Alene Tchekmedyian contributed to this report from Los Angeles and Sandra Dibble, a staff writer for the San Diego Union-Tribune, from Tijuana.